A silvery metal is put inside a beaker of water. Bubbles form on the surface of the metal, and it dissolves gradually. (b) Do you expect the remaining solution to be a pure substance or a mixture?

Name: Chemistry: The Central Science
Author: Brown
ISBN: 9780134414232

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Identify the metal: The problem describes a metal reacting with water, which is a common characteristic of alkali metals like sodium or potassium. These metals react with water to form a hydroxide and hydrogen gas, which explains the bubbles.

Understand the reaction: When an alkali metal reacts with water, it forms a metal hydroxide and releases hydrogen gas. For example, sodium reacts with water to form sodium hydroxide (NaOH) and hydrogen gas (H₂).

Analyze the solution: After the reaction, the metal hydroxide dissolves in water, creating an aqueous solution. This solution contains water and the dissolved metal hydroxide.

Define pure substance and mixture: A pure substance consists of only one type of particle, either an element or a compound. A mixture contains two or more different substances that are not chemically bonded.

Determine the nature of the solution: Since the solution contains both water and dissolved metal hydroxide, it is a mixture. The presence of more than one type of particle (water molecules and hydroxide ions) classifies it as a mixture, not a pure substance.

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Chemical Reactions

When a metal reacts with water, it undergoes a chemical reaction, often resulting in the formation of a hydroxide and hydrogen gas. This process can lead to the dissolution of the metal, which is characterized by the formation of bubbles as hydrogen gas is released. Understanding this reaction is crucial to predicting the nature of the resulting solution.

Pure Substances vs. Mixtures

A pure substance consists of only one type of particle and has a uniform composition, while a mixture contains two or more different substances that retain their individual properties. In the context of the question, the reaction of the metal with water produces a solution that contains dissolved metal ions and possibly other components, indicating that the solution is a mixture rather than a pure substance.

Solubility

Solubility refers to the ability of a substance to dissolve in a solvent, forming a homogeneous solution. In this scenario, the metal's gradual dissolution in water suggests that it is soluble in water, contributing to the formation of a mixture. The extent of solubility can vary significantly among different metals, affecting the composition of the resulting solution.